Lexmark C 746 Service Manual

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925.02, 925.04, 925.06—Cartridge cooling fan error service check
31. Disconnect the cable in connector JFAN1, 
and install a new fan.
2. Turn the multifunction printer off, and turn 
the MFP on (perform a POR).
Note: After installing the new fan, a print test 
is required to verify operation. Print one page 
every 30 seconds for 20 minutes to test the 
highest fan speed. Do not test unless the fan 
is installed in the machine.
Did the error...

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945.xx, 947.xx—Transfer roll error service check
Step Questions / actions Yes No
11. Replace the transfer module. See 
“Transfer module removal” on 
page 4-171. 
2. POR the printer.
Note: Print 5 pages one at a time to check 
operation.
Did the error clear?Problem resolved. Replace the original 
transfer module. Go to step 
2.
2Turn the printer off, and then remove the rear 
frame cover. See “Rear frame cover 
removal” on page 4-47. 
Check the cable in...

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4Remove the HVPS. See “High-voltage 
power supply (HVPS) removal” on 
page 4-115. Check for continuity between the 
contacts (yellow1 and yellow2, cyan1 and 
cyan2, magenta1 and magenta2, or black1 
and black2) on the transfer contact assembly. Go to step 4. Replace the transfer 
contact assembly.
Is continuity present?
4 Replace the HVPS. See “High-voltage 
power supply (HVPS) removal” on 
page 4-115. 
Does the error clear?Problem resolved. Replace...

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950.00–950.29—EPROM mismatch failure
Warning:When replacing any one of the following components:
•System board
•Operator assembly card or top access cover assembly
Replace only one component at a time or the printer will be rendered inoperable. Replace the required 
component, bring the printer up in Diagnostic menu (see “Diagnostics menu” on page 3-2), and verify that the 
problem is fixed before performing a POR.
This error code indicates a mismatch...

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Next956.xx—System board failure service check
6Replace the operator panel assembly. See 
“Operator panel assembly removal 
(C746)” on page 4-34 or “Operator panel 
assembly removal (C748)” on page 4-37.
Is the error message still displayed?Replace the system board. 
See “System board 
removal” on page 4-155. Problem resolved.
Step Questions / actions Yes No
1Turn the printer off, and remove the rear 
frame cover. See “Rear frame cover 
removal” on page...

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5 V interlock switch service check
Step Questions / actions Yes No
1Is the +5 V interlock switch damaged? Replace the 5 V interlock 
switch. See “5 V interlock 
switch cable removal” on 
page 4-61.Go to step 2.
2Turn the printer off, and remove the rear 
frame cover. See “Rear frame cover 
removal” on page 4-47.
Check the cable in connector JINT1 for 
proper connection to the system board, for 
pinch points, and for any other damage to the 
cable or...

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24 V interlock switch service check
Step Questions / actions Yes No
1Is the 24 V interlock switch damaged? Replace the 24 V interlock 
switch. See “24 V 
interlock switch removal” 
on page 4-63.Go to step 2.
2Turn the printer off, and remove the rear 
frame cover. See “Rear frame cover 
removal” on page 4-47.
Check the cable in connector JCVR1 for 
proper connection to the system board, for 
pinch points, and for any other damage to the 
cable or...

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Bubble sensor service check
Step Questions / actions Yes No
1Is the bubble sensor flag damaged? Replace the fuser. See 
“Fuser removal” on 
page 4-110.Go to step 2.
2Remove the rear frame cover. See “Rear 
frame cover removal” on page 4-47.
Check the fuser DC cable in connector 
JFUSER1 for proper connection to the system 
board, pinch points, and any other damage to 
the cable or connector.
Is the cable damaged?Replace the fuser DC 
cable. See “Fuser DC...

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51. Replace the fuser.
2. Bring the printer up in Diagnostics Menu 
(turn off the printer, press and hold 
buttons 3 and 6, then turn on the printer).
3. Navigate to SENSOR TESTS > Dynamic 
Sensors > Bubble.
4. Open the front door.
5. Activate the bubble sensor.
Did the bubble sensor change from Open to 
Closed?Problem resolved. Replace the system board. 
See “System board 
removal” on page 4-155. Step Questions / actions Yes No 

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Dead printer service check
A dead printer is a condition where the display is blank, the LED on the operator panel is off, no fans turn, no 
motors turn, and the fuser lamp does not come on.
If a 550-sheet option assembly is installed, remove the option and check the base printer for correct operation. If 
the base printer operates correctly, replace the 550-sheet option assembly.
Warning:Observe all necessary ESD precautions when removing and handling the...